The present invention relates to a sealing device and, more particularly, to a sealing device which suffers from reduced wear and which is capable of improving sealing effect.
In general, a sealing device is disposed between a stationary part and a rotary shaft such that the sealing device is penetrated by the rotary shaft so as to provide a seal in the gap between the rotary shaft and the stationary part. FIGS. 4 to 6 illustrate the construction of a typical example of the sealing device of the kind described.
The sealing device shown in these Figures has a slinger 43 composed of a tubular portion 43b through which the rotary shaft 41 extends and a radial portion 43a provided on one axial end of the tubular portion 43b and extending radially outwardly therefrom, and a rubber seal 45 which is disposed on the outer side of the tubular portion 43b of the slinger 43. The rubber seal 45 has a reinforcement member 44 embedded therein. The reinforcement member has a substantially L-shaped cross-section with one leg 44a thereof being directed towards the slinger 43.
The rubber seal 45 has outer peripheral surface fitting in the bore in the stationary part 42, and is provided, at its portion near the end of the reinforcement member 44 adjacent the slinger 43, with a lip 45a contacting the radial portion 43a of the slinger 43 and a lip 45b which is directed towards the tubular portion 43b on the rotary shaft 41.
In order to impart a high oil-gathering effect produced by the lips 45a and 45b, a spiral groove 46 starting at the center and terminating at the peripheral end is formed in the surface of the radial portion 43a of the slinger 43 facing the lip 45a.
In operation, the slinger 43 rotates together with the rotary shaft 41 as a unit therewith, with the lip 45a of the rubber seal 45 keeping a sliding contact with the radial portion 43a of the slinger 43 thereby attaining a sealing effect.
This known sealing device, however, suffers from the following disadvantages.
In operation, the spiral groove 46 formed in the radial portion 43a of the slinger 43 serves to displace the oil radially outwardly during rotation of the slinger 43 as shown in FIG. 6. In addition, the pressure at which the lip 45a contacts with the slinger 43 is kept constant regardless of the rotation speed 41 of the rotary shaft 41. In consequence, the lip 45a is rapidly worn down due to sliding contact with the radial portion 43a of the slinger 43 during rotation of the rotary shaft 41, thus impairing durability of the sealing device, and the load torque is undesirably increased as the rotation speed increases.